Hard coating film and optical elements having such coating film

Abstract

A hard coating film is disclosed which is formed by hardening a coating composition containing the following component A and/or component B and component C: Component A: an organosilicon compound or a hydrolyzate thereof, said organosilicon compound being represented by the formula (I): (R.sup.1).sub.a (R.sup.3).sub.b Si(OR.sup.2).sub.4-(a+b) (I) Component B: an organosilicon compound or a hydrolyzate thereof, said organosilicon compound being represented by the formula (II): ##STR1## Component C: fine particles of tin oxide having a particle size of 1 to 100 millimicrons and coated with fine particles of tungsten oxide. The coating film is excellent in hot water resistance and transparency and finds particularly useful application to lenses for spectacles.

What is claimed is: 
     
       1. A coating film on a substrate formed by hardening a coating composition containing component C and component A or component B or components A, B and C, wherein component A is: an organosilicon compound or a hydrolyzate thereof, said organosilicon compound being represented by the formula (I):   (R.sup.1).sub.a (R.sup.3).sub.b Si(OR.sup.2).sub.4-(a+b)   (I)        wherein R 1  and R 3  are each an organic group containing therein at least one member selected from the group consisting of an alkyl group, alkenyl group, aryl group, acyl group, halogen group, glycidoxy group, epoxy group, amino group, mercapto group, methacryloxy group and cyano group; R 2  is a member selected from the group consisting of alkyl group having 1 to 8 carbon atoms, alkoxy group having 1 to 8 carbon atoms, acyl group having 1 to 8 carbon atoms and phenyl group; and a and b are each integers of 0 or 1;   component B is: an organosilicon compound or a hydrolyzate thereof, said organosilicon compound represented by the formula (II): ##STR4##  wherein R 4  is an organic group having 1 to 5 carbon atoms; X is an alkyl group having 1 to 4 carbon atoms or an acyl group having 1 to 4 carbon atoms; Y is an organic group having 2 to 20 carbon atoms; and a is an integer of 0 or 1 and;   component C is: particles of tin oxide having a particle size of 0.1 to 30 millimicrons and coated with fine particles of tungsten oxide in a weight ratio of tungsten oxide particles to tin oxide particles of 0.005 to 0.5 wherein the amount of solid portion of the tin oxide particles coated with the tungsten oxide particles is in the range of 0.02 to 5 parts to 1 part of the organosilicon compound or a hydrolyzate thereof used as component A, component B or both component A and component B.   
     
     
       2. A coating film according to claim 1, wherein the organosilicon compound used as component A is a mixture of a trialkoxysilane compound of the formula (I) wherein R 2  is an alkyl group having 1 to 4 carbon atoms, a is 1 and b is 0, with a dialkoxysilane compound of the formula (I) wherein R 2  is an alkyl group having 1 to 4 carbon atoms, a is 1 and b is also 1. 
     
     
       3. A coating film according to claim 1, wherein the surfaces of the tin oxide particles coated with the tungsten oxide particles are negatively charged. 
     
     
       4. A coating film according to claim 1, wherein said coating composition further contains particles of a metal oxide selected from the group consisting of silicon oxide, antimony oxide, titanium oxide, cerium oxide, aluminum oxide and zirconium oxide. 
     
     
       5. A coating film according to claim 1, wherein said coating composition further contains one or more of organic amines selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine. 
     
     
       6. A coating film according to claim 1, wherein said coating composition contains one or more of organic acids selected from the group consisting of tartaric acid, citric acid and amino-acids. 
     
     
       7. A coating film according to claim 1, wherein the pH of said coating composition is in the range of 1 to 6. 
     
     
       8. A coating film according to claim 1, wherein said coating composition contains one or more of hardening catalysts selected from the group consisting of metal alkoxides, metal chelates and metal salts. 
     
     
       9. An optical element having a coating film which comprises a base material and a coating film provided thereon, said coating film formed by hardening a coating composition containing component C and component A or component B or components A and B and C, which are specified below, wherein component A is: an organosilicon compound or a hydrolyzate thereof, said organosilicon compound being represented by the formula (I):   (R.sup.1).sub.a (R.sup.3).sub.b Si(OR.sup.2).sub.4-(a+b)   (I)        wherein R 1  and R 3  are each an organic group containing therein at least one member selected from the group consisting of an alkyl group, alkenyl group, aryl group, acyl group, halogen group, glycidoxy group, epoxy group, amino group, mercapto group, methacryloxy group and cyano group; R 2  is a member selected from the group consisting of alkyl group having 1 to 8 carbon atoms, alkoxy group having 1 to 8 carbon atoms, acyl group having 1 to 8 carbon atoms and phenyl group; and a and b are each integers of 0 or 1;   component B is: an organosilicon compound or a hydrolyzate thereof, said organosilicon compound represented by the formula (II): ##STR5##  wherein R 4  is an organic group having 1 to 5 carbon atoms; X is an alkyl group having 1 to 4 carbon atoms or an acyl group having 1 to 4 carbon atoms; Y is an organic group having 2 to 20 carbon atoms; and a is an integer of 0 or 1; and   component C is: particles of tin oxide having a particle size of 0.1 to 30 millimicrons and coated with fine particles of tungsten oxide in a weight ratio of tungsten oxide particles to tin oxide particles of 0.005 to 0.5 wherein the amount of solid portion of the tin oxide particles coated with the tungsten oxide particles is in the range of 0.02 to 5 parts to 1 part of the organosilicon compound or a hydrolyzate thereof used as component A, component B or both component A and component B.   
     
     
       10. An optical element having a coating film according to claim 9, wherein the organic silicon compound used as component A of the coating composition is a mixture of a trialkoxysilane compound of the formula (I) wherein R 2  is an alkyl group having 1 to 4 carbon atoms, a is 1 and b is 0, with a dialkoxysilane compound of the formula (I) wherein R 2  is an alkyl group having 1 to 4 carbon atoms, a is 1 and b is also 1. 
     
     
       11. An optical element having a coating film according to claim 9, wherein the tin oxide particles coated with the tungsten oxide particles, used as component C, are negatively charged on their surfaces. 
     
     
       12. An optical element having a coating film according to claim 9, wherein the base material is a lens for spectacles. 
     
     
       13. An optical element having a coating film according to claim 9, wherein an anti-reflection film is formed on said hard coating film.